The present invention relates to a differential-current switch.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
Differential-current switches are known in which a differential current which is determined or detected is digitized by means of an analog-to-digital converter, and is further processed and evaluated by means of digital signal processing. The disadvantageous aspect in such differential-current switches is that they resolve the occurring differential currents only insufficiently, at least in the actually implemented configurations. A resolution of 100 μA is necessary at a nominal differential current of 30 mA. With the currently used analog-to-digital converters which have a resolution of 10 bits or 12 bits, such a fine resolution is only possible at a considerable limitation of the maximum resolvable differential current, which is why overdriving (clipping) occurs at high differential currents.
Differential-current switches are also known which in addition to an line-voltage-independent electronic trigger system comprises an line-voltage-dependent electronic trigger system. It is known that the line-voltage-dependent electronic trigger system is activated once the supply voltage exceeds a predetermined threshold value. The disadvantageous aspect in such differential-current switches is that defective line-voltage-dependent electronic trigger systems are “activated” when the conditions concerning the supply voltage are fulfilled, though which such a differential-current switch does not fulfill the intended protective function.
By using analog-to-digital converters of a higher resolution (analog-to-digital converters with a resolution of at least 20 bits or, even better, 24 bits would be required here), a resolution of the differential current signal would be possible even in the case of a very large differential currents, e.g. in the magnitude of some ten to 100 amperes. However, this represents a very costly and uneconomical solution because in addition to the very costly high-resolution analog-to-digital converters the further components of the digital signal processing would have to be adapted to the high data rates as a result of the resolution, through which costs would rise even further.
It would therefore be desirable and advantageous to address prior art shortcomings and to provide a differential-current switch, with which a favorable resolution of a differential current signal over a wide dynamic range can be achieved by substantially avoiding overdriving, which increases the readiness and security of differential-current switches with line-voltage-dependent electronic trigger systems, and which offers low component costs.